The present invention relates to a semiconductor integrated circuit having a program control circuit for writing data into a serial EEPROM.
In a known method of exchanging signals between a CPU and a serial EEPROM, the CPU sends a chip-select signal CS, a serial clock signal SK, and memory write data DI to the EEPROM, while the EEPROM sends memory readout data DO to the CPU, as shown in FIG. 2.
With the prior art method, if the CPU gets out of control, signals more than the number of clocks necessary for the memory program are transferred to the EEPROM. As a result, unwanted data is written to the memory.
In order to solve this problem with the prior art techniques, it is an object of the present invention to prevent erroneous writing by ignoring writing instructions when signals other than a given number of clocks necessary for a program are entered.